A new BLSA study of Prostate Growth and Disease was begun in February 1993 to examine anatomic and physiologic correlates of normal prostate growth and the development and progression of benign prostatic hyperplasia and prostate cancer. In the past year, four studies have been completed. The first BLSA study showed that the epithelial composition of the prostates of men with benign prostatic hyperplasia (BPH) was positively correlated with PSA level and PSA velocity. Thus, PSA could be useful as an inexpensive method of targeting drug treatments at either the epithelial or stromal components of BPH. The second study demonstrated that the variability in PSA levels was similar in men with BPH whether the samples were drawn at 3 month, 6 month, or 2 year intervals. This documented for the first time that prostate cancer screening criteria based on rate of change in PSA are affected by the testing interval. The third study compared the sensitivity and specificity of several different candidate PSA criteria for the detection of prostate cancer. Average PSA velocity had the highest combined sensitivity and specificity of all the criteria compared. The fourth study retrospectively examined serum androgen levels in men with and without prostate cancer. No significant differences were observed in age-adjusted luteinizing hormone, total testosterone, sex-hormone binding globulin, or free testosterone levels. These findings suggest that serum testosterone levels are not a strong risk factor for the development of prostate cancer.